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Abstract:
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The enemy release hypothesis predicts that invasive plant species may benefit from a top- down control by co-evolved herbivores, particularly specialists, in their new range. However, to benefit from enemy escape, invasive plants must also escape or resist specialist or generalist herbivores that attack related species in the introduced range. We compared damage on the exotic invasive Lonicera maackii with the native congener Lonicera reticulata, and the native confamilial Viburnum prunifolium growing in the field. We also tested the laboratory performance of a North American honeysuckle specialist sawfly and a widespread generalist caterpillar on two North American native and two Asian exotic Lonicera species. Lonicera maackii received significantly lower amounts of foliar herbivory as compared to L. reticulata and V. prunifolium. Native L. reticulata was heavily damaged by the specialist in the field, but was not detected on non-native L. maackii. In no- choice feeding assays, the specialist herbivore performed best on native L. reticulata, while the generalist herbivore performed best on non- native L. maackii. Exotic L. japonica experienced little herbivory in the field and was unpalatable to the specialist, while the generalist had low overall survival, but high growth rates of the surviving larvae. Both exotic species experienced little herbivory in the field, but L. maackii appears to escape detection by the specialist, while L. japonica is highly resistant to it. These findings indicate that enemy escape contributes to the success of exotic Lonicera species. |
